The present invention relates to a process for alkylation of an isoparaffin with an olefin, especially alkylation of isobutane with butene over the solid acid catalysts.
In petroleum-chemical industry, as well known in the art, concentrated sulfuric acid and hydrofluoric acid catalysts are widely used in the process of isoparaffin-olefin alkylation, especially in alkylation of isobutane with butene, in order to produce higher molecular weight alkylates with high octane rating, as valuable gasoline blending components. However, both sulfuric acid and hydrofluoric acid share inherent drawbacks including equipment corrosion problem, serious environment and safety concerns. A lot of efforts have been directed to developing solid acid alkylation process to substitute for sulfuric acid or hydrofluoric acid processes.
In the past, new solid acid catalysts for the above alkylation process have been widely investigated and reported. For example, JP 01, 245, 853, U.S. Pat. Nos. 3,962,133 and 4,116,880, GB 1,432,720 and GB 1,389,237, etc. disclose SO42xe2x88x92 enhanced super acid catalysts; U.S. Pat. Nos. 5,220,095, 5,731,256, 5,489,729, 5,364,976, 5,288,685 and EP 0,714,871A, etc. disclose CF3SO3H/silica catalysts; U.S. Pat. Nos. 5,391,527, and 5,739,074, etc. disclose Ptxe2x80x94AlCl3xe2x80x94KCl/Al2O3 catalysts; U.S. Pat. Nos. 5,157,196, 5,190,904, 5,346,676, 5,221,777, 5,120,897, 5,245,101, 5,012,033, 5,157,197, CN 1,062,307A and WO 95,126,815, etc. disclose Lewis acid catalysts, such as SbF5, BF3 and AlCl3; CN1, 184,797A, U.S. Pat. Nos. 5,324,881 and 5,475,178, etc. disclose supported heteropoly acid catalysts; U.S. Pat. Nos. 3,917,738 and 4,384,161, etc. disclose molecular sieve catalysts.
The most serious problem existing in the solid acid alkylation process is that the catalysts deactivate very quickly during the reaction. For example, the deactivation of some molecular sieve catalysts and SO42xe2x88x92/oxide catalysts occurs very quickly, in a few hours or even less than an hour, and the activity and selectivity of catalysts reduce dramatically resulting in the decline in the octane number of alkylate. Therefore, the regeneration of the solid acid alkylation catalysts has become a problem demanding prompt solution in the development of the solid acid alkylation process.
Presently, some kinds of hydrocarbon conversion reaction using solid acid catalysts, such as alkylation, isomerization, oligomerization and hydro-isomerization, are carried out at lower temperatures, wherein the macromolecular paraffins or olefins deposited on the surface of catalysts due to certain the side reactions, such as polymerization of olefin and hydride transference. These heavy hydrocarbons are organic compounds with a C/H ratio of less than 1, known as coke precursors, which are different from those coke substances with a C/H ratio of more than 1 originating in the reactions of hydrocarbon conversion at higher temperature, such as catalytic reforming and fluid catalytic cracking.
U.S. Pat. No. 5,365,010 discloses a process for regeneration of solid acid alkylation catalysts by calcination at high temperatures. In this process, Lewis acid catalysts, especially the BF3 supported on alumina (BF3/AI2O3), are calcinated at 600xc2x0 C. in order to burn out the heavy hydrocarbons deposited on the surface of the catalysts. High temperature regeneration is only applicable to the catalysts having good high temperature stability.
U.S. Pat. No. 5,326,923 and CN 1,076,386A disclose a process for regeneration of hydrocarbon conversion catalysts comprising contacting supported Lewis acid catalysts with solvent SO2 in order to remove the reaction deposits from the surface of the catalysts, and to reactivate the catalysts.
JP 8-281,118 discloses a method for regeneration of solid heteropoly acid catalysts, comprising extracting the solid heteropoly acid or salt alkylation catalysts outside the reactor at normal temperature and pressure with polar or non-polar solvents in order to reactivate the catalyst partly. The non-polar solvents of C4-C10 saturated fatty hydrocarbons are stated in the claims, but only polar solvents are used in the examples.
U.S. Pat. No. 3,855,343 discloses an isoparaffin-olefin alkylation process carried out in a slurry-phase reactor, comprising contacting isoparaffin with olefin in the presence of a BF3-containing cation-exchange resin catalyst and regenerating the catalyst by extraction with polar solvents.
U.S. Pat. No. 5,489,732 discloses a moving-bed alkylation process in which the catalysts are regenerated by the following method: dividing the exhausted catalyst equally into two parts, regenerating one part of the catalysts with the liquid-phase isoparaffin feedstock containing dissolved H2 and regenerating the other part of the catalysts with H2 at high temperature, then combining the two parts of used catalysts and separating hydrogen out, then mixing with the feedstock and recycling into the reactor for alkylation.
U.S. Pat. No. 5,523,503 discloses a solid acid catalyst alkylation process using the cocurrent simulated moving-bed. The process is carried out in several beds divided into reaction zone and regeneration zone; in which the position of reaction zone and regeneration zone is changed by controlling the inlet points of the feedstocks and regeneration stream, thus the purpose of continuous reaction-and-regeneration is realized by the cycle of such switching-over. Wherein the feedstock in reaction zone passes through at least two catalyst beds, that is, the reaction effluent containing unreacted feedstock and products from the first reaction bed enters the second bed, or then enters the third bed. The solvent for regeneration of the catalyst is the liquid-phase isoparaffin feedstock containing dissolved H2. In the process hydrogen needs to be separated. Moreover, there is at least one bed undergoing regeneration at any one time.
An object of the present invention is to provide an isoparaffin-olefin alkylation process to produce alkylated oils with high octane number, wherein the continuous alkylation reaction can be realized and at the same time the catalyst can be regenerated effectively to resume its alkylation activity and selectivity by a simple operational process without a regeneration zone undergoing regeneration at any one time.
The present invention provides a process for alkylation of isoparaffin with olefin using a solid acid catalyst, comprising:
Feeding an alkylation feedstock comprising isoparaffin and C3xcx9cC6 mono-olefins into at least two parallel reactors the reaction under conditions for alkylation in presence of a solid acid catalyst;
When the selectivity and activity of the catalyst in one or more of said reactors or the octane number of alkylate from the bottom descends due to macromolecular hydrocarbons deposited on the surface of the catalyst, switching said one or more reactors over to feed a solvent stream for regeneration of the catalyst to carry out the solvent extraction for regeneration of the catalyst in situ, and after the regeneration transferring the used solvent stream to the solvent-recovery unit for reuse;
Switching said one or more reactors over after the completion of the regeneration to feed said alkylation feedstock to continue the alkylation again;
Wherein the alkylation is being carried out in at least one of all reactors during the process.
The invention provides a process for alkylation of isoparaffin with olefin over a solid acid catalyst. In the present process, the catalyst is regenerated in situ with a solvent, and at least two parallel reactors are used at the same time, each of which is charged with said catalyst and can be used for alkylation. Either the alkylation feedstock or the solvent for regeneration can pass through the inlet of each reactor by switching over the valves, and either the reaction effluent or the used solvent can pass through the outlet of each reactor to the fractionating tower of reaction products or to the recovery tank of recycling used solvents respectively by switching over the valves. The process can be described, as follows: Alkylation feedstock comprising isoparaffin and C3xcx9cC6 mono-olefins is fed into each reactor to carry out the reaction under the conditions for alkylation and then the reaction effluent flows into the fractionating tower, where the reaction products are separated out and the unreacted isoparaffin from the top of tower is circulated back to the reactors; when the selectivity and activity of catalyst in one or more of said reactors or the octane number of alkylates from the bottom descends due to macromolecular hydrocarbons deposited on the surface of the catalyst, said one or more reactors is/are switched over to feed a solvent stream for regeneration of the catalyst to carry out the regeneration-extraction of the catalyst, and thereafter the used solvent is transferred to the solvent-recovery tank, and as the regeneration is completed, said one or more reactors is/are switched over to feed the alkylation feedstock to carry out the alkylation again. The alkylation is carried out in at least one of said reactors during the process.
According to the process provided by the present invention, preferably, said isoparaffin is isobutane and said C3xcx9cC6 mono-olefin is butene.
According to the process provided by the present invention, said catalyst is a solid acid catalyst used widely in the prior art for alkylation of low-carbon isoparaffins with C3xcx9cC6 mono-olefins, such as supported heteropoly acid and salt catalysts, zeolite molecular sieve catalysts, SO42xe2x88x92/oxide super acid catalysts, supported conjugated Brxc3x6nsted-Lewis solid super acid catalysts, ion-exchange resin catalysts and Lewis acid-treated oxide or molecular sieve catalysts, etc. Since the deposits on the surface of the solid acid catalyst which cause the catalyst deactivation are the coke precursors with a C/H ratio of less than 1, a person having ordinary skill in the art is not difficult to understand that all the solid acid catalysts used for the alkylation of low-carbon isoparaffins with olefins can be regenerated by the process according to the present invention, so it is unnecessary to specify the catalysts particularly. Preferably the catalyst is one selected from the supported heteropoly acids catalyst, supported conjugated Brxc3x6nsted-Lewis solid super acid catalysts or solid polymerized ion-exchange resin catalysts; and most preferably it is supported heteropoly acids catalysts.
According to the process provided by the present invention, said supported heteropoly acids catalyst comprises a porous inorganic supporter and a heteropoly acid having a chemical formula of H8xe2x88x92n[AM12O40], wherein A is phosphorus atom or silicon atom, M is tungsten atom or molybdenum atom, n is the number of valence state of A, being 4 or 5; said porous inorganic supporter material is a conventional one selected from the group consisting of active carbon, silica, alumina, magnesia, titanium oxide, crude or synthetical zeolites, carbon fiber and clay or mixtures thereof. Preferably it is selected from silica, alumina or the mixture thereof.
According to the process provided by the present invention, said supported conjugated Brxc3x6nsted-Lewis solid super acid catalyst preferably comprises a porous inorganic supporter material of 40-95 wt %, a heteropoly acid of 1-60 wt % and a Lewis acid of 0.3xcx9c15 wt % supported thereon; said heteropoly acid and porous inorganic supporter material are the same as the ones defined in supported heteropoly acid catalysts as above; said Lewis acid is one selected from AICI3, BF3 or XF5, wherein X is P, As, Sb, or Bi.
According to the process provided by, the present invention, said other catalysts are conventional solid acid catalysts disclosed in the prior art for alkylation of low-carbon isoparaffins with olefins, and are not particularly specified in this invention.
According to the process provided by the present invention, said solvent for regeneration can be selected from a wide range of solvents, preferably at least one of non-polar solvents selected from the group including C4xcx9cC20 saturated fatty hydrocarbons and aromatics, etc., more preferably isobutane or C4-C16 saturated fatty hydrocarbons, and most preferably C5-C12 saturated fatty hydrocarbons, and/or at least one of polar solvents selected from the group including alcohols, phenols, ethers, esters, halide alkanes and CS2, etc.; more preferably C2-C8 alcohols, C2-C8 esters or C1-C4 halide alkanes. It is worth mentioning that a non-polar solvent should be used for the regeneration of supported heteropoly acid alkylation catalysts because heteropoly acid may possibly be dissolved in a polar solvent.
According to the process provided by the present invention, said conditions for alkylation are those adopted widely in the alkylation process, preferably the supercritical reaction conditions, which include: a reaction temperature in the range of from the supercritical temperature of isoparaffin to 300xc2x0 C., preferably from the supercritical temperature of isoparaffin to 250xc2x0 C., and more preferably from the supercritical temperature of isoparaffin to 200xc2x0 C.; a reaction pressure in the range of from the supercritical pressure of isoparaffin to 10.0 MPa, preferably from the supercritical pressure of isoparaffin to 9.0 MPa, and more preferably from the supercritical pressure of isoparaffin to 6.0 MPa; a mole ratio of isoparaffin to olefin in the range of 2.0xcx9c100, preferably 10xcx9c90; and a WHSV of feed in the range of 0.1xcx9c20 hrxe2x88x921, preferably 0.5xcx9c8 hrxe2x88x921.
According to the process provided by the preset invention, said process of solvent extraction of regeneration of the catalyst comprises separating the alkylation feedstock and catalyst in reactor, then introducing the solvent stream into the reactor and washing in-suit the catalysts with said solvent for 0.2xcx9c24 hrs, preferably 0.5xcx9c15 hrs under the conditions of temperature 25xcx9c300xc2x0 C., preferably 50xcx9c200xc2x0 C., pressure 0xcx9c8.0 MPa, preferably 0.2xcx9c6.0 MPa, and WHSV 0.1xcx9c20.0 hrxe2x88x921, preferably 0.5xcx9c8.0 hrxe2x88x92.
According to the present invention, the process for alkylation of isoparaffin with olefin can be carried out in all kinds of reactors, such as the fixed-bed , batch-bed, moving-bed, and fluidized-bed reactors or the tri-phase slurry bed reactor, etc. The feedstock can flow either upward or downward.
The amount of extraction solvent used should be sufficient for totally or partly washing out the macromolecular hydrocarbons deposited on the surface of catalyst, which are organic compounds with C/H ratio less than 1. According to our study, it is learned that said macromolecular hydrocarbons deposited on the surface of the supported heteropoly acid alkylation catalyst are made up of C13xcx9cC25 saturated alkanes and a trace of polynuclear aromatic hydrocarbons.